The present invention relates to humidifiers and more particularly to a method and apparatus for controlling the humidity in a chamber.
Humidifiers of various types are known. Some, which may be termed evaporative humidifiers, depend largely or entirely on relative movement between air to be humidified and a water bearing surface. These include, for example, units wherein water is thrown from a high speed rotating wheel and rapidly enters the atmosphere as finely divided droplets, or wherein a moving air stream is directed past or through water bearing screens or porous members. Disadvantages of these humidifiers include the undesirable distribution of water droplets carrying dust, bacteria and other contaminates from the water supply. Also, frequent cleaning maintenance is required not only for the evaporation unit itself but also for the environmental surfaces contacted by the thus humidified air.
Humidifiers of another type humidify by heating water to generate steam for admission to the atmosphere. Minerals in the water supply remain in the heated water reservoir and are not admitted to the humidified air. Moreover the boiling of the supply water to produce steam substantially kills bacteria, and therefore a clean, sterile water vapor is distributed to the environment.
One problem associated with boiling a quantity of water relates to the long lead time taken to increase the amount of water vapor generated and the long lead time required to stop the flow of water vapor when no longer needed. Thus such systems are not well adapted to precise control of humidity, particularly in a small chamber wherein only small amounts of water vapor are to be added in order to achieve a proper humidity level.